package config_test

import (
	"bytes"
	"encoding/json"
	"log/slog"
	"maps"
	"net/netip"
	"os"
	"slices"
	"strings"
	"testing"
	"time"

	"sneak.berlin/go/smallwebwaf/internal/config"
)

// The settings, by name.
const (
	listenAddr              = "SWWAF_LISTEN_ADDR"
	upstreamURL             = "SWWAF_UPSTREAM_URL"
	mode                    = "SWWAF_MODE"
	trustedProxies          = "SWWAF_TRUSTED_PROXIES"
	clientRequestTimeout    = "SWWAF_CLIENT_REQUEST_TIMEOUT"
	clientHeaderMaxBytes    = "SWWAF_CLIENT_REQUEST_HEADER_MAX_BYTES"
	clientIdleTimeout       = "SWWAF_CLIENT_IDLE_TIMEOUT"
	clientResponseTimeout   = "SWWAF_CLIENT_RESPONSE_TIMEOUT"
	upstreamRequestTimeout  = "SWWAF_UPSTREAM_REQUEST_TIMEOUT"
	upstreamResponseTimeout = "SWWAF_UPSTREAM_RESPONSE_TIMEOUT"
	requestMaxBytes         = "SWWAF_REQUEST_MAX_BYTES"
	responseMaxBytes        = "SWWAF_RESPONSE_MAX_BYTES"
	allowNets               = "SWWAF_ALLOW_NETS"
	rateLimitExemptNets     = "SWWAF_RATE_LIMIT_EXEMPT_NETS"
	denyNets                = "SWWAF_DENY_NETS"
	rateLimitPerMinute      = "SWWAF_RATE_LIMIT_PER_MINUTE"
	rateLimitPerHour        = "SWWAF_RATE_LIMIT_PER_HOUR"
	rateLimitPerDay         = "SWWAF_RATE_LIMIT_PER_DAY"
	deniedCountries         = "SWWAF_DENIED_COUNTRIES"
	allowedCountries        = "SWWAF_EXCLUSIVELY_ALLOWED_COUNTRIES"
	banResponse             = "SWWAF_BAN_RESPONSE"
	limitBanDuration        = "SWWAF_LIMIT_BAN_DURATION"
	limitBanRepeatWindow    = "SWWAF_LIMIT_BAN_REPEAT_WINDOW"
	maxBanDuration          = "SWWAF_MAX_BAN_DURATION"
	maxBans                 = "SWWAF_MAX_BANS"
	banScopeV4Prefix        = "SWWAF_BAN_SCOPE_V4_PREFIX"
	stateDir                = "SWWAF_STATE_DIR"
	stateWriteDelay         = "SWWAF_STATE_WRITE_DELAY"
	stateCounterInterval    = "SWWAF_STATE_COUNTER_INTERVAL"
	metricsToken            = "SWWAF_METRICS_TOKEN" //nolint:gosec // the setting's name
	metricsTopN             = "SWWAF_METRICS_TOP_N"
	instanceName            = "SWWAF_INSTANCE_NAME"
	logRequestHeaders       = "SWWAF_LOG_REQUEST_HEADERS"
)

// defaultLogRequestHeaders is the default of SWWAF_LOG_REQUEST_HEADERS.
const defaultLogRequestHeaders = "accept,accept-language,accept-encoding," +
	"content-type,origin,range"

// token is a token of 32 characters, the shortest allowed.
const token = "0123456789abcdef0123456789abcdef"

// off switches a timeout, a size limit or a rate limit off.
const off = "off"

// environment is a set of environment variables, for FromEnvironment.
type environment map[string]string

// lookupEnv reads one of the variables, as os.LookupEnv does.
func (e environment) lookupEnv(name string) (string, bool) {
	value, ok := e[name]

	return value, ok
}

// fromEnvironment reads the settings from env, which must be valid.
func fromEnvironment(t *testing.T, env environment) *config.Config {
	t.Helper()

	cfg, err := config.FromEnvironment(env.lookupEnv)
	if err != nil {
		t.Fatalf("settings %v: %v", env, err)
	}

	return cfg
}

func TestDefaults(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{})

	wantSettings(t, cfg, config.Config{
		ListenAddr:                  ":8080",
		Observe:                     false,
		ClientRequestTimeout:        time.Minute,
		ClientRequestHeaderMaxBytes: 32 << 10,
		ClientIdleTimeout:           2 * time.Minute,
		ClientResponseTimeout:       30 * time.Minute,
		UpstreamRequestTimeout:      time.Minute,
		UpstreamResponseTimeout:     30 * time.Minute,
		RequestMaxBytes:             100 << 20,
		ResponseMaxBytes:            5 << 30,
		RateLimitPerMinute:          1000,
		RateLimitPerHour:            10000,
		RateLimitPerDay:             50000,
		BanResponse:                 403,
		LimitBanDuration:            time.Hour,
		LimitBanRepeatWindow:        24 * time.Hour,
		MaxBanDuration:              7 * 24 * time.Hour,
		MaxBans:                     5000,
		BanScopeV4Prefix:            32,
		StateDir:                    "/var/lib/smallwebwaf",
		StateWriteDelay:             10 * time.Second,
		StateCounterInterval:        15 * time.Minute,
		MetricsToken:                "",
		MetricsTopN:                 50,
	})

	if cfg.UpstreamURL.String() != "http://127.0.0.1:8081" {
		t.Errorf("%s is %s", upstreamURL, cfg.UpstreamURL)
	}

	wantNetblocks(t, cfg.TrustedProxies,
		"10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16")
	wantNetblocks(t, cfg.AllowNets)
	wantNetblocks(t, cfg.RateLimitExemptNets)
	wantNetblocks(t, cfg.DenyNets)
	wantCountries(t, deniedCountries, cfg.DeniedCountries)
	wantCountries(t, allowedCountries, cfg.ExclusivelyAllowedCountries)

	hostname, err := os.Hostname()
	if err != nil || hostname == "" || cfg.InstanceName != hostname {
		t.Errorf("%s is %q, want the host's name %q (%v)", instanceName,
			cfg.InstanceName, hostname, err)
	}

	wantHeaders := strings.Split(defaultLogRequestHeaders, ",")
	if !slices.Equal(cfg.LogRequestHeaders, wantHeaders) {
		t.Errorf("%s gave %v, want %v", logRequestHeaders, cfg.LogRequestHeaders,
			wantHeaders)
	}
}

func TestValuesAsSet(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{
		listenAddr:              "127.0.0.1:9000",
		upstreamURL:             "https://app.internal:8443/",
		mode:                    "observe",
		trustedProxies:          " 192.0.2.1, 10.1.2.3/8 ,2001:db8::/32",
		clientRequestTimeout:    "90s",
		clientHeaderMaxBytes:    "8K",
		clientIdleTimeout:       "5m",
		clientResponseTimeout:   "7d",
		upstreamRequestTimeout:  "1h30m",
		upstreamResponseTimeout: off,
		requestMaxBytes:         "512K",
		responseMaxBytes:        "1234",
		allowNets:               "192.0.2.7",
		rateLimitExemptNets:     "2001:db8::/48, 10.9.8.7",
		denyNets:                "198.51.100.0/24",
		rateLimitPerMinute:      "60",
		rateLimitPerHour:        "600",
		rateLimitPerDay:         "6000",
		deniedCountries:         "cn, RU,kp,Xk",
		allowedCountries:        "de",
		banResponse:             "429",
		limitBanDuration:        "15m",
		limitBanRepeatWindow:    "2d",
		maxBanDuration:          "30d",
		maxBans:                 "100",
		banScopeV4Prefix:        "24",
		stateDir:                "/srv/waf-state",
		stateWriteDelay:         "500ms",
		stateCounterInterval:    "1h",
		metricsToken:            token,
		metricsTopN:             "10",
	})

	wantSettings(t, cfg, config.Config{
		ListenAddr:                  "127.0.0.1:9000",
		Observe:                     true,
		ClientRequestTimeout:        90 * time.Second,
		ClientRequestHeaderMaxBytes: 8 << 10,
		ClientIdleTimeout:           5 * time.Minute,
		ClientResponseTimeout:       7 * 24 * time.Hour,
		UpstreamRequestTimeout:      90 * time.Minute,
		UpstreamResponseTimeout:     0,
		RequestMaxBytes:             512 << 10,
		ResponseMaxBytes:            1234,
		RateLimitPerMinute:          60,
		RateLimitPerHour:            600,
		RateLimitPerDay:             6000,
		BanResponse:                 429,
		LimitBanDuration:            15 * time.Minute,
		LimitBanRepeatWindow:        48 * time.Hour,
		MaxBanDuration:              30 * 24 * time.Hour,
		MaxBans:                     100,
		BanScopeV4Prefix:            24,
		StateDir:                    "/srv/waf-state",
		StateWriteDelay:             500 * time.Millisecond,
		StateCounterInterval:        time.Hour,
		MetricsToken:                token,
		MetricsTopN:                 10,
	})

	if cfg.UpstreamURL.String() != "https://app.internal:8443/" {
		t.Errorf("%s is %s", upstreamURL, cfg.UpstreamURL)
	}

	wantNetblocks(t, cfg.TrustedProxies, "192.0.2.1/32", "10.0.0.0/8", "2001:db8::/32")
	wantNetblocks(t, cfg.AllowNets, "192.0.2.7/32")
	wantNetblocks(t, cfg.RateLimitExemptNets, "2001:db8::/48", "10.9.8.7/32")
	wantNetblocks(t, cfg.DenyNets, "198.51.100.0/24")
	wantCountries(t, deniedCountries, cfg.DeniedCountries, "CN", "RU", "KP", "XK")
	wantCountries(t, allowedCountries, cfg.ExclusivelyAllowedCountries, "DE")
}

func TestInstanceNameAndLoggedHeadersAsSet(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{
		instanceName:      "fsn1app1/gitea",
		logRequestHeaders: " Accept , X-Custom",
	})

	if cfg.InstanceName != "fsn1app1/gitea" ||
		!slices.Equal(cfg.LogRequestHeaders, []string{"accept", "x-custom"}) {
		t.Errorf("%s is %q and %s gives %v", instanceName, cfg.InstanceName,
			logRequestHeaders, cfg.LogRequestHeaders)
	}
}

func TestCodeOnBothCountryListsStopsTheStart(t *testing.T) {
	t.Parallel()

	_, err := config.FromEnvironment(environment{
		deniedCountries:  "cn,ru",
		allowedCountries: "de,RU",
	}.lookupEnv)
	if err == nil {
		t.Fatal("ru on both country lists was accepted")
	}

	if !strings.HasPrefix(err.Error(), allowedCountries+": ") ||
		!strings.Contains(err.Error(), `"RU"`) {
		t.Errorf("error %q does not name %s and RU", err, allowedCountries)
	}
}

func TestSizesAndOff(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{
		requestMaxBytes:      "3G",
		responseMaxBytes:     off,
		clientRequestTimeout: off,
		clientIdleTimeout:    off,
	})

	if cfg.RequestMaxBytes != 3<<30 || cfg.ResponseMaxBytes != 0 ||
		cfg.ClientRequestTimeout != 0 || cfg.ClientIdleTimeout != 0 {
		t.Errorf("3G, off, off and off read as %d, %d, %s and %s",
			cfg.RequestMaxBytes, cfg.ResponseMaxBytes, cfg.ClientRequestTimeout,
			cfg.ClientIdleTimeout)
	}
}

func TestRequestHeaderMaxBytesJustOver4K(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{clientHeaderMaxBytes: "4097"})
	if cfg.ClientRequestHeaderMaxBytes != 4097 {
		t.Errorf("4097 read as %d", cfg.ClientRequestHeaderMaxBytes)
	}
}

func TestRequestHeaderMaxBytesRefusalNeverOffersOff(t *testing.T) {
	t.Parallel()

	for _, value := range []string{"32KB", "0", "4K", off} {
		t.Run(value, func(t *testing.T) {
			t.Parallel()

			_, err := config.FromEnvironment(
				environment{clientHeaderMaxBytes: value}.lookupEnv)

			want := clientHeaderMaxBytes + `: "` + value +
				`" is not a size of more than 4K, such as 32K`
			if err == nil || err.Error() != want {
				t.Errorf("error %v, want %s", err, want)
			}
		})
	}
}

func TestRateLimitsOff(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{
		rateLimitPerMinute: off,
		rateLimitPerHour:   off,
		rateLimitPerDay:    off,
	})

	if cfg.RateLimitPerMinute != 0 || cfg.RateLimitPerHour != 0 ||
		cfg.RateLimitPerDay != 0 {
		t.Errorf("off read as %d, %d and %d",
			cfg.RateLimitPerMinute, cfg.RateLimitPerHour, cfg.RateLimitPerDay)
	}
}

func TestBanResponseCloseIsZero(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{banResponse: "close"})
	if cfg.BanResponse != 0 {
		t.Errorf("close read as %d, want 0", cfg.BanResponse)
	}
}

func TestTrustedProxiesSetButEmptyTrustNothing(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{trustedProxies: ""})
	if len(cfg.TrustedProxies) != 0 {
		t.Errorf("trusted proxies %v, want none", cfg.TrustedProxies)
	}
}

func TestInvalidValueStopsTheStart(t *testing.T) {
	t.Parallel()

	for _, tc := range []struct{ name, value string }{
		{listenAddr, "8080"}, {listenAddr, ":http"}, {listenAddr, ":65536"},
		{upstreamURL, "127.0.0.1:8081"},
		{upstreamURL, "ftp://127.0.0.1:8081"},
		{upstreamURL, "http://"},
		{upstreamURL, "http://:8081"},
		{upstreamURL, "http://127.0.0.1:0"},
		{upstreamURL, "http://127.0.0.1:99999"},
		{upstreamURL, "http://127.0.0.1:8081/app"},
		{upstreamURL, "http://127.0.0.1:8081/?a=1"},
		{upstreamURL, "http://user:secret@127.0.0.1:8081"},
		{mode, "Observe"}, {mode, "block"}, {mode, ""},
		{trustedProxies, "10.0.0.0/33"},
		{trustedProxies, "traefik"},
		{trustedProxies, "10.0.0.0/8,,192.168.0.0/16"},
		{trustedProxies, "fe80::1%eth0"},
		{allowNets, "192.0.2.0/24,monitoring"},
		{rateLimitExemptNets, "2001:db8::/129"},
		{denyNets, "198.51.100.0/24,"},
		{clientRequestTimeout, "60"}, {clientRequestTimeout, ""},
		{clientIdleTimeout, "0s"},
		{clientIdleTimeout, "2 minutes"},
		{clientResponseTimeout, "1y"},
		{upstreamRequestTimeout, "-1s"},
		{upstreamResponseTimeout, "0s"},
		{upstreamResponseTimeout, "1.5d"},
		{requestMaxBytes, "100MB"},
		{requestMaxBytes, "100m"},
		{requestMaxBytes, "1.5M"},
		{responseMaxBytes, "0"},
		{responseMaxBytes, "-5"},
		{responseMaxBytes, "99999999999G"},
		{rateLimitPerMinute, ""},
		{rateLimitPerMinute, "1K"},
		{rateLimitPerHour, "0"},
		{rateLimitPerHour, "1.5"},
		{rateLimitPerDay, "-1"},
		{rateLimitPerDay, "lots"},
		{deniedCountries, "nk"},
		{deniedCountries, "kp,,ir"},
		{deniedCountries, "prk"},
		{deniedCountries, "408"},
		{deniedCountries, "k"},
		{deniedCountries, "eu"},
		{deniedCountries, "un"},
		{deniedCountries, "su"},
		{allowedCountries, "ac"},
		{allowedCountries, "uk"},
		{allowedCountries, "zz"},
		{allowedCountries, "de,germany"},
		{banResponse, "404"}, {banResponse, "drop"}, {banResponse, ""},
		{limitBanDuration, off}, {limitBanDuration, "0s"}, {limitBanDuration, "1"},
		{limitBanRepeatWindow, off}, {limitBanRepeatWindow, "-1h"},
		{maxBanDuration, off}, {maxBanDuration, "1w"},
		{maxBans, off}, {maxBans, "0"}, {maxBans, "5K"},
		{banScopeV4Prefix, "33"}, {banScopeV4Prefix, "-1"}, {banScopeV4Prefix, "/24"},
		{stateDir, ""}, {stateDir, "state"}, {stateDir, "./var/lib/smallwebwaf"},
		{stateWriteDelay, off}, {stateWriteDelay, "0s"},
		{stateCounterInterval, off}, {stateCounterInterval, "15"},
		{metricsTopN, off}, {metricsTopN, "0"}, {metricsTopN, "-1"},
		{logRequestHeaders, "accept,,origin"}, {logRequestHeaders, "accept;origin"},
		{logRequestHeaders, "accept language"}, {logRequestHeaders, "x-foo:"},
		{logRequestHeaders, "host"}, {logRequestHeaders, "accept,Host"},
		{logRequestHeaders, "transfer-encoding"}, {logRequestHeaders, "TRANSFER-ENCODING"},
	} {
		t.Run(tc.name+"="+tc.value, func(t *testing.T) {
			t.Parallel()

			_, err := config.FromEnvironment(environment{tc.name: tc.value}.lookupEnv)
			if err == nil {
				t.Fatalf("%s=%q was accepted", tc.name, tc.value)
			}

			if !strings.HasPrefix(err.Error(), tc.name+": ") {
				t.Errorf("error %q does not name %s", err, tc.name)
			}
		})
	}
}

func TestHostOrTransferEncodingStopsTheStart(t *testing.T) {
	t.Parallel()

	// Only Host's message points to the field host.
	for value, want := range map[string]string{
		"Host": `"Host" is taken out of every request by Go's HTTP server, ` +
			"so it can never be logged; the request's host is the field host",
		"transfer-encoding": `"transfer-encoding" is taken out of every ` +
			"request by Go's HTTP server, so it can never be logged",
	} {
		t.Run(value, func(t *testing.T) {
			t.Parallel()

			_, err := config.FromEnvironment(environment{logRequestHeaders: value}.lookupEnv)
			if err == nil || err.Error() != logRequestHeaders+": "+want {
				t.Errorf("error %v, want %s: %s", err, logRequestHeaders, want)
			}
		})
	}
}

func TestShortTokenStopsTheStartWithoutShowingIt(t *testing.T) {
	t.Parallel()

	// Characters are counted, not bytes: each é takes two.
	for _, value := range []string{"", token[1:], strings.Repeat("é", 31)} {
		t.Run(value, func(t *testing.T) {
			t.Parallel()

			_, err := config.FromEnvironment(environment{metricsToken: value}.lookupEnv)

			want := metricsToken + ": is shorter than 32 characters"
			if err == nil || err.Error() != want {
				t.Errorf("error %v, want %s", err, want)
			}
		})
	}
}

func TestTokenIsLoggedMasked(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{metricsToken: token})

	var out bytes.Buffer

	slog.New(slog.NewJSONHandler(&out, nil)).Info("starting", "settings", cfg)

	if strings.Contains(out.String(), token) ||
		!strings.Contains(out.String(), `"`+metricsToken+`":"********"`) {
		t.Errorf("the token is not logged masked: %s", out.String())
	}
}

func TestLogsEachSettingWithItsValue(t *testing.T) {
	t.Parallel()

	cfg := fromEnvironment(t, environment{clientRequestTimeout: "45s"})

	var out bytes.Buffer

	slog.New(slog.NewJSONHandler(&out, nil)).Info("starting", "settings", cfg)

	var line struct {
		Settings map[string]string `json:"settings"`
	}

	err := json.Unmarshal(out.Bytes(), &line)
	if err != nil {
		t.Fatalf("decode %s: %v", out.Bytes(), err)
	}

	hostname, _ := os.Hostname()

	want := map[string]string{
		listenAddr:              ":8080",
		upstreamURL:             "http://127.0.0.1:8081",
		mode:                    "enforce",
		trustedProxies:          "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16",
		clientRequestTimeout:    "45s",
		clientHeaderMaxBytes:    "32K",
		clientIdleTimeout:       "120s",
		clientResponseTimeout:   "30m",
		upstreamRequestTimeout:  "60s",
		upstreamResponseTimeout: "30m",
		requestMaxBytes:         "100M",
		responseMaxBytes:        "5G",
		allowNets:               "",
		rateLimitExemptNets:     "",
		denyNets:                "",
		rateLimitPerMinute:      "1000",
		rateLimitPerHour:        "10000",
		rateLimitPerDay:         "50000",
		deniedCountries:         "",
		allowedCountries:        "",
		banResponse:             "403",
		limitBanDuration:        "1h",
		limitBanRepeatWindow:    "24h",
		maxBanDuration:          "7d",
		maxBans:                 "5000",
		banScopeV4Prefix:        "32",
		stateDir:                "/var/lib/smallwebwaf",
		stateWriteDelay:         "10s",
		stateCounterInterval:    "15m",
		metricsToken:            "",
		metricsTopN:             "50",
		instanceName:            hostname,
		logRequestHeaders:       defaultLogRequestHeaders,
	}
	if !maps.Equal(line.Settings, want) {
		t.Errorf("logged settings\n%v\nwant\n%v", line.Settings, want)
	}
}

// wantSettings checks the settings that are plain values.
func wantSettings(t *testing.T, got *config.Config, want config.Config) {
	t.Helper()

	if got.ListenAddr != want.ListenAddr ||
		got.Observe != want.Observe ||
		got.ClientRequestTimeout != want.ClientRequestTimeout ||
		got.ClientRequestHeaderMaxBytes != want.ClientRequestHeaderMaxBytes ||
		got.ClientIdleTimeout != want.ClientIdleTimeout ||
		got.ClientResponseTimeout != want.ClientResponseTimeout ||
		got.UpstreamRequestTimeout != want.UpstreamRequestTimeout ||
		got.UpstreamResponseTimeout != want.UpstreamResponseTimeout ||
		got.RequestMaxBytes != want.RequestMaxBytes ||
		got.ResponseMaxBytes != want.ResponseMaxBytes ||
		got.RateLimitPerMinute != want.RateLimitPerMinute ||
		got.RateLimitPerHour != want.RateLimitPerHour ||
		got.RateLimitPerDay != want.RateLimitPerDay {
		t.Errorf("settings\n%+v\nwant\n%+v", got, want)
	}

	wantBanSettings(t, got, want)
}

// wantBanSettings checks the settings for bans, the state files and the
// metrics.
func wantBanSettings(t *testing.T, got *config.Config, want config.Config) {
	t.Helper()

	if got.BanResponse != want.BanResponse ||
		got.LimitBanDuration != want.LimitBanDuration ||
		got.LimitBanRepeatWindow != want.LimitBanRepeatWindow ||
		got.MaxBanDuration != want.MaxBanDuration ||
		got.MaxBans != want.MaxBans ||
		got.BanScopeV4Prefix != want.BanScopeV4Prefix {
		t.Errorf("ban settings\n%+v\nwant\n%+v", got, want)
	}

	if got.StateDir != want.StateDir ||
		got.StateWriteDelay != want.StateWriteDelay ||
		got.StateCounterInterval != want.StateCounterInterval {
		t.Errorf("state settings\n%+v\nwant\n%+v", got, want)
	}

	if got.MetricsToken != want.MetricsToken || got.MetricsTopN != want.MetricsTopN {
		t.Errorf("metrics token %q and top %d, want %q and %d",
			got.MetricsToken, got.MetricsTopN, want.MetricsToken, want.MetricsTopN)
	}
}

// wantNetblocks checks a list of netblocks.
func wantNetblocks(t *testing.T, got []netip.Prefix, want ...string) {
	t.Helper()

	gotText := make([]string, 0, len(got))
	for _, netblock := range got {
		gotText = append(gotText, netblock.String())
	}

	if !slices.Equal(gotText, want) {
		t.Errorf("netblocks %v, want %v", gotText, want)
	}
}

// wantCountries checks the list of countries the setting name gave.
func wantCountries(t *testing.T, name string, got []string, want ...string) {
	t.Helper()

	if !slices.Equal(got, want) {
		t.Errorf("%s gave %v, want %v", name, got, want)
	}
}